Modulation of glucose transport in fetal rat lung: a sexual dimorphism

Sex hormones and macronutrient metabolism

The biological differences between males and females are determined by a different set of genes and by a different reactivity to environmental stimuli, including the diet, in general. These differences are further emphasized and driven by the exposure to a different hormone flux throughout the life.

These differences have not been taken into appropriate consideration by the scientific community. Nutritional sciences are not immune from this “bias” and when nutritional needs are concerned, females are considered only when pregnant, lactating or when their hormonal profile is returning back to “normal,” i.e., to the male-like profile.

The authors highlight some of the most evident differences in aspects of biology that are associated with nutrition.

This review presents and describes available data addressing differences and similarities of the “reference man” vs. the “reference woman” in term of metabolic activity and nutritional needs. According to this assumption, available evidences of sex-associated differences of specific biochemical pathways involved in substrate metabolism are reported and discussed. The modulation by sexual hormones affecting glucose, amino acid and protein metabolism and the metabolization of nutritional fats and the distribution of fat depots, is considered targeting a tentative starting up background for a gender concerned nutritional science.

Obesity-Associated Inflammatory Cytokines and Prostaglandin E2 Stimulate Glucose Transporter mRNA Expression and Glucose Uptake in Primary Human Adipose Stromal Cells

Obesity is associated with chronic low-grade inflammation. This occurs largely as a result of the infiltration of immune cells within the obese adipose, which produce a number of inflammatory factors, including interleukin-6 (IL-6), IL-1β, tumor necrosis factor-α (TNFα), and prostaglandin E(2) (PGE(2)). These factors have previously been shown to affect insulin-mediated glucose uptake in differentiated adipocytes. However, the insulin-independent effect of inflammation on adipocyte precursors, the adipose stromal cells, has not been explored. This study therefore aimed to examine the effect of obesity-associated inflammatory factors on the expression of insulin-independent glucose transporters (GLUT1 and GLUT3) and on the uptake of glucose within adipose stromal cells. Primary human subcutaneous adipose stromal cells were isolated from abdominoplasty, and the effect of inflammatory cytokines (IL-6, IL-1β, and TNFα) and PGE(2) on GLUT mRNA expression and glucose transport was assessed using real-time polymerase chain reaction and radiolabeled deoxyglucose uptake assays, respectively. Results demonstrate that all four inflammatory mediators caused a dose-dependent increase in GLUT1 mRNA expression and glucose uptake. GLUT3 mRNA expression was also upregulated by IL-6 (0.5 ng/mL), TNFα (0.1 and 10 ng/mL), and PGE(2) (0.1 μM). Overall, these results demonstrate that obesity-associated inflammation increases insulin-independent glucose transporter expression and glucose uptake in undifferentiated adipose stromal cells.

Identification of estrogen target genes during zebrafish embryonic development through transcriptomic analysis

Estrogen signaling is important for vertebrate embryonic development. Here we have used zebrafish (Danio rerio) as a vertebrate model to analyze estrogen signaling during development. Zebrafish embryos were exposed to 1 µM 17β-estradiol (E2) or vehicle from 3 hours to 4 days post fertilization (dpf), harvested at 1, 2, 3 and 4 dpf, and subjected to RNA extraction for transcriptome analysis using microarrays. Differentially expressed genes by E2-treatment were analyzed with hierarchical clustering followed by biological process and tissue enrichment analysis. Markedly distinct sets of genes were up and down-regulated by E2 at the four different time points. Among these genes, only the well-known estrogenic marker vtg1 was co-regulated at all time points. Despite this, the biological functional categories targeted by E2 were relatively similar throughout zebrafish development. According to knowledge-based tissue enrichment, estrogen responsive genes were clustered mainly in the liver, pancreas and brain. This was in line with the developmental dynamics of estrogen-target tissues that were visualized using transgenic zebrafish containing estrogen responsive elements driving the expression of GFP (Tg(5xERE:GFP)). Finally, the identified embryonic estrogen-responsive genes were compared to already published estrogen-responsive genes identified in male adult zebrafish (Gene Expression Omnibus database). The expressions of a few genes were co-regulated by E2 in both embryonic and adult zebrafish. These could potentially be used as estrogenic biomarkers for exposure to estrogens or estrogenic endocrine disruptors in zebrafish. In conclusion, our data suggests that estrogen effects on early embryonic zebrafish development are stage- and tissue- specific.

Fetal adrenal gland alterations in a rat model of adverse intrauterine environment

By feeding a low-sodium diet to dams over the last third of gestation, we have developed an animal model of intrauterine growth restriction (IUGR). Given that fetal adrenal development and maturation occur during late gestation in rats, the aim of this study was to evaluate the expression of proteins and enzymes involved in steroidogenesis and catecholamine synthesis in adrenal glands from IUGR fetuses. A gene microarray was performed to investigate for alteration in the pathways participating in hormone production. Results show that increased aldosterone serum concentrations in IUGR fetuses were associated with higher mRNA adrenal levels of angiotensin II receptor type 1 (AT(1)R) and cytochrome P450 aldosterone synthase in response to decreased serum sodium content. Conversely, reduced serum corticosterone concentrations in these fetuses appear to result from alterations in gene expression involved in cholesterol metabolism, such as the augmented apolipoprotein E levels, and in steroidogenesis, like the decreased levels of cytochrome P45011beta-hydroxylase. Furthermore, increased AT(2)R expression and the presence of hypoxia and oxidative stress may, in turn, explain the higher adrenal mRNA levels of enzymes involved in catecholamine synthesis. Despite this increase, catecholamine adrenal content was reduced in males and was similar in females compared with sex-matched controls, suggesting higher catecholamine secretion. This could be associated with the induction of genes involved in inflammation-related, acute-phase response in IUGR fetuses. All of these alterations could have long-lasting health effects and may, hence, be implicated in the pathogenesis of increased blood pressure and cardiac hypertrophy observed in IUGR adult animals from this model.

Metabolic modulators following trauma sepsis: Sex hormones

BACKGROUND

The development of metabolic perturbations following severe trauma/sepsis leading to decreased energy production, hyperglycemia, and lipolysis is often rapid. Gender is increasingly recognized as a major factor in the outcome of patients suffering from trauma/sepsis. Moreover, sex hormones influence energy, glucose, and lipid metabolism. Metabolic modulators, such as peroxisome proliferator-activated receptor-gamma coactivator-1 and peroxisome proliferator-activated receptor-alpha, which are required for mitochondrial energy production and fatty acid oxidation, are regulated by the estrogen receptor-beta and consequently contribute to cardioprotection following trauma hemorrhage. Additionally, sex steroids regulate inflammatory cytokines that cause hypermetabolism/catabolism via acute phase response, leading to increased morbidity and mortality.

MEASUREMENTS

This article examines the following: (1) the evidence for gender differences; (2) energy, glucose, and lipid metabolism and the acute phase protein response; (3) the mechanisms by which gender/sex hormones affect the metabolic modulators; and (4) the tissue-specific effect of sex hormone receptors and the effect of genomic and nongenomic pathways of sex hormones following trauma.

RESULTS AND CONCLUSIONS

The available information indicates that sex steroids not only modulate the immune/cardiovascular responses but also influence various metabolic processes following trauma. Thus, alteration or modulation of the prevailing hormone milieu at the time of injury appears to be a novel therapeutic adjunct for improving outcome after injury.

Efecto del retardo de crecimiento intrauterino sobre el dimorfismo sexual en recien nacidos de termino: una adaptación prenatal en perspectiva evolutiva

OBJETIVOS: identificar si se modifica el dismorfismo sexual del crecimiento frente a retardo de crecimiento intrauterino. MÉTODOS: se compararon 4931 recién nacidos con (n=497) y sin (n=4434) retardo de crecimiento intrauterino. Todos fueron de término (para Argentina >37 semanas). La población se dividió en dos grupos de acuerdo a la condición de crecimiento fetal y el sexo. Los indicadores antropométricos del crecimiento prenatal incluyeron el peso corporal, la longitud y el perímetro cefálico. RESULTADOS: no hubo diferencias estadísticas significativas entre sexos en el peso al nacer y la longitud corporal en neonatos con retardo de crecimiento intrauterino. De forma contraria, los neonatos con crecimiento fetal normal evidenciaron diferencias significativas en ambos indicadores entre sexos siendo más grandes los varones. CONCLUSIONES: la inhibición del dismorfismo sexual está ya presente en etapas prenatales cuando ocurre una situación que afecte el crecimiento como es el caso del retardo de crecimiento intrauterino. Se considera la perspectiva evolutiva de dicho fenómeno inhibitorio.

Gender difference in the Oatp1-mediated tubular reabsorption of estradiol 17beta-D-glucuronide in rats

The gender difference in the urinary excretion of estradiol-17beta-glucuronide (E(2)-17betaG) was examined in rats. The urinary clearance of E(2)-17betaG was >250 times lower in male than in female rats. No such major gender difference was observed in its biliary excretion or metabolism in kidney homogenate. Both plasma protein binding and inulin clearance were comparable in male and female rats, suggesting that this gender difference cannot be explained by glomerular filtration. The urinary clearance with respect to the plasma unbound E(2)-17betaG in male rats was <1% of the glomerular filtration rate, indicating its potential reabsorption by the kidney, and this increased to a level comparable with that found in female rats when dibromosulfophthalein was coinfused. A marked increase in E(2)-17betaG urinary excretion was also observed in male rats that had undergone orchidectomy. Testosterone injections given to female rats reduced the urinary excretion to a level comparable with that of control male rats. The concomitant change in the expression of the gene product for organic anion-transporting polypeptide Oatp1, of which E(2)-17betaG is a typical substrate, was found in the kidney membrane fractions after these treatments. These results suggest that urinary E(2)-17betaG excretion is subject to hormonal regulation and that the large gender difference can be explained by regulation in Oatp1-mediated reabsorption.

Embryonic epithelial membrane transporters

Embryonic epithelial membrane transporters are organized into transporter families that are functional in several epithelial organs, namely, in kidney, lung, pancreas, intestine, and salivary gland. Family members (subtypes) are developmentally expressed in plasma membranes in temporospatial patterns that are 1) similar for one subtype within different organs, like aquaporin-1 (AQP1) in lung and kidney; 2) different between subtypes within the same organ, like the amiloride-sensitive epithelial sodium channel (ENaC) in lung; and 3) apparently matched among members of different transporter families, as alpha-ENaC with AQP1 and -4 in lung and with AQP2 in kidney. Finally, comparison of temporal expression patterns in early embryonic development of transporters from different families [e.g., cystic fibrosis transmembrane conductance regulator (CFTR), ENaC, and outer medullary potassium channel] suggests regulatory activating or inactivating interactions in defined morphogenic periods. This review focuses on embryonic patterns, at the mRNA and immunoprotein level, of the following transporter entities expressed in epithelial cell plasma membranes: ENaC; the chloride transporters CFTR, ClC-2, bumetanide-sensitive Na-K-Cl cotransporter, Cl/OH, and Cl/HCO(3); the sodium glucose transporter-glucose transporter; the sodium/hydrogen exchanger; the sodium-phosphate cotransporter; the ATPases; and AQP. The purpose of this article is to relate temporal and spatial expression patterns in embryonic and in early postnatal epithelia to developmental changes in organ structure and function.

Identification of sex-specific differences in surfactant synthesis in rat lung

Delayed lung maturation and lower levels of surfactant phosphatidylcholine have been previously identified in male fetuses compared with female fetuses in several species. We investigated the mechanisms for sex differences in surfactant content by examining parameters of phosphatidylcholine turnover and biosynthesis; the latter was evaluated by measuring metabolic steps within the biosynthetic pathway. Compared with male lung cells, freshly isolated lung cells from female fetuses contained higher levels of disaturated phosphatidylcholine, a marker of surfactant lipid. Female mixed monolayer cultures exhibited a 71% increase in choline incorporation into disaturated phosphatidylcholine compared with male cultures. Male cultures exhibited significantly greater release of [3H]-arachidonic acid into the medium compared with females, suggesting sex differences in phospholipase activity. However, pulse-chase studies showed no sex differences in degradation of disaturated phosphatidylcholine, which was confirmed by assays of phospholipase A2, phosphatidylcholine-specific phospholipase C, and phospholipase D. Female mixed lung cells, however, had greater rates of cellular choline transport and activity of cytidylyltransferase, the rate-regulatory enzyme for phosphatidylcholine synthesis. Separate studies showed that exposure of sex-specific pretype II cell cultures to cortisol-stimulated fibroblast-conditioned medium plus transforming growth factor-beta-neutralizing antibody stimulated cytidylyltransferase activity to a greater extent in male cells compared with female cells. These studies indicate that sex differences in surfactant phospholipid content are not due to differences in phospholipid turnover, but rather differential regulation of specific metabolic steps within the surfactant biosynthetic pathway. The data also support a role for transforming growth factor-beta as a negative regulator of a key surfactant biosynthetic enzyme within male lungs.